An embryologist might say gastrulation, which is when an embryo can no longer divide to form identical twins. A neuroscientist might say when one can measure brainwaves. Roe v. Wade allows abortion up to the point a fetus is viable outside the womb. But that's not much help, either. But earlier this year, Bell published a paper in the New England Journal of Medicine showing reasonably good outcomes in preemies born at 22 weeks of gestational age. Two key technologies have pushed that date: the use of steroids, which can speed up fetal development, and surfactants that prevent lungs from collapsing after birth.
Still, setting an absolute cutoff for fetal viability is impossible. Is it some babies survive? Half survive? Or most babies survive? Finally, it was with the advent of the cell theory developed by Schleiden and Schwann in that it was recognized that the embryo develops from the single-celled zygote. It is a process of change and growth that transforms the zygote, a single cell, into a multicellular adult human being.
Eberl goes on to say — and this is really the debate:. In the last century, and particularly in the last decades, much more detailed observation has been made of the first 24 hours of the life of a human being. During this time the cell membranes of a sperm and ovum fuse and the first cell division occurs.
When during this 24 hours does, a new human life begin? Embryologists are less united on this question. This Statement aims to clarify this issue. During the first 24 hours, once the sperm and egg bind to each other, the membranes of these two cells fuse, creating in less than a second a single hybrid cell: the zygote, or one-cell embryo.
Finally, the nuclear membranes of the pronuclei break down called syngamy—technically, pronuclear membranes. No new nuclear membrane encompassing both pronuclei is formed; rather, mitosis occurs and two cells, each with its own identical nucleus encased in a nuclear membrane, are formed. Furthermore, studies with mice embryos demonstrate that despite the plasticity of which allows disrupted blastomeres to form an entire organism, ordinarily the polarity of the embryo is determined by the site of sperm penetration.
Some embryologists consider fertilization a day-long process and regard the beginning of human life as occurring near the end of this process at syngamy, 1,18,21 whereas others consider the time of cell membrane fusion when the embryo gives evidence of being a different kind of cell than either oocyte or sperm, to be the beginning of a new human life, since within minutes the new embryo acts to prevent the merger of another sperm with itself and starts the business of self-replication.
The single-celled embryo is a very different kind of cell than that of sperm or oocyte, and contains a unique genome that will determine most future bodily features and functions of his or her lifetime.
It is clear that from the time of cell fusion, the embryo consists of elements from both maternal and paternal origin which function interdependently in a coordinated manner to carry on the function of the development of the human organism. From this definition, the single-celled embryo is not just a cell, but an organism, a living being, a human being.
In contrast to human embryos, human cells are alive and, under some circumstances, they can assemble into primitive tissues and structures. Yet under no circumstances do mere human cells produce the kind of coordinated interactions necessary for building a fully integrated human body. They do not produce tissues in a coherent manner and do not organize them so as to sustain the life of the entity as a whole. They produce tumors; i. They behave like cells , not like organisms. The conclusion that human life begins at sperm-egg fusion is uncontested, objective, based on the universally accepted scientific method of distinguishing different cell types from each other and on ample scientific evidence thousands of independent, peer-reviewed publications.
Moreover, it is entirely independent of any specific ethical, moral, political, or religious view of human life or of human embryos.
Indeed, this definition does not directly address the central ethical question surrounding the embryo: What value ought society place on human life at the earliest stages of development? A scientific perspective. Totipotency; What it is and what it is not. You are you. You get this DNA at conception. Well, so what? They didn't look at Nature, science proceedings, National Academy of Sciences. They looked in Cosmopolitan, Vogue, Redbook, Newsweek. They asked the question, how is DNA being represented?
They found that it was being represented as the secular equivalent of soul. First it was that which is your essence, as that Stand Up Girl said. It is that which your determines your behaviors, as Ramsey and Stand Up Girl said.
It's that from which you an be resurrected after death, a la Jurassic Park. We are uniquely who we are at conception. The DNA is sacred, and it's so pervasive in our culture that you'd be amazed. If I were to ask you do cars have DNA? You'd probably say no.
But you'd be wrong. DNA is become the metaphor for our essence, for that which makes you you, so even cars, when they do their advertising, a Sterling's remarkably handling is "in its genes", a Subaru is a "genetic superstar", Toyota "has a great set of genes", and "The new Nissan designed DNA is evident". DNA is become essence. Here's the most recent one. Smaller chromosomes. The culture of America believes that DNA is our essence. Can't find it there. Our antibodies won't see it.
It's in the soul of every Finn, and this notion of DNA is soul just is rampant through our literature, but we know scientifically this is not so. Doctor Jones and others talked yesterday about epigenetics. Here we see two genetically identical mice. They do not look genetically identical. Their mothers were given different diets.
The different diets actually activated and suppressed different genes, so one is obese and golden, the other is sleek and brown, so the genes are not determining their obesity in this case. The genes are not determining their color. It's the environment, the maternal diet that's doing this. I'm not going to go into this slide, but maternal care can activate or repress gene expression in rats.
Here we see the glucocorticoid receptor in the brain of rats, and depending on whether the rats got maternal care during the first seven days of postnatal life, you either activate or un-activate this particular gene. In both cases, this is due to DNA methylation, this epigenetic phenomena. We even get a separate inheritance.
We get bacteria. As we go through the reproductive tract of the female, we get new bacteria. That bacteria colonizes our gut. Our gut expects it. We get variation. We get finished by the bacteria that we inherit, often through birth. So the new syllabus would say that we are not determined to be essentially who or what we are at fertilization.
Many of our fundamental bodily behavioral characters are not determined by genes, but by the environment. The second error, and this is a quotation from C. Ward Kischer, who is the chairman of the American Advisory Council for Bioethics, a Catholic organization, says, "From the first moment of conception, human development is a fait accompli under conditions which we have come to understand and embrace as NORMAL.
I wish this were true, but certainly obstetricians and gynecologists know all too well that the fetus is not safe, the embryo is not safe within the womb, and that most conceptions, most fertilization events do not come to term as babies, and Michael Sandel when he was brought before the President's Commission on Bioethics said, "If the embryo lost that accompanies natural procreation were the moral equivalent of infant death," in other words, if the zygote is a person, "then pregnancy would have to be regarded as a public health crisis of epidemic proportions: Alleviating natural embryo loss would be a more urgent moral cause than abortion, in vitro fertilization, and stem cell research combined.
We know drugs, chemical teratogens, the endocrine disruptors, bisphenol A causes myotic abnormalities in the embryonic mice. BPA exposure in utero predisposes rat mammary glands to have cancers later in life. These are important things. The fetus is not safe. It doesn't come to term normally. Matter of fact, a majority of conceptions do not. Current technological society's increasing the risk that babies will with be born with anomalies, fertility problems, and susceptibilities to disease, as Doctor Jones mentioned yesterday.
Moreover, these anomalies and disease susceptibilities we now know can be transferred through the DNA, through these DNA methylation changes, these epigenetic changes to children and grandchildren.
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